MIL-DTL-6162 Generators And Starter-Generators, Electrical Direct Current, Nominal 30 Volts, Aircraft General Specification ForThis specification covers the general requirements for aircraft generators and starter-generators for use in 28-volt \(V\) direct current \(DC\) systems. As generators, both type machines are engine driven. The starter-generators, however, also function as engine starters when energized by electric power.

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MIL-DTL-6162C

4.6.9.1 Exciting current. The machine shall be connected into the test setup and operated as a generator over

the speed range. For any speed or load within the range, field current shall increase with an increase in load. Unless

otherwise specified in the associated specification sheet, the field current shall not exceed 8 amperes at any speed

between the minimum and maximum speed for regulation. At any rated speed, the external field resistance shall not

be required to dissipate more than 90 watts.

Upon completion of the above test, the generator residual voltage shall be measured with the generator

operating at the minimum rated speed and the shunt field circuit open. The residual voltage shall not be less than

+ 0.8 volts.

4.6.9.2 Residual field. The generator shall be operated with an approved voltage regulator to furnish power

through a reverse current relay to a 15-ampere resistive load in parallel with a fully charged 34-ampere hour nickel

cadmium battery. The generator shall be operated until the battery charging current is less than 10 amperes at 28.0

volts. The voltage regulator power lead shall be interrupted to de-energize the generator. The generator shall be

automatically disconnected from the load bus by the operation of the reverse current relay. The generator residual

voltage shall be measured without further generator operation. The residual voltage shall not reverse its polarity and

shall not be less than 0.8 volts with the generator speed at the specified minimum rated.

4.6.10 Ripple voltage. The machine shall be operated as a generator under the conditions specified in

paragraph 4.6.12.2. The ripple voltage appearing on the d-c output shall be measured using a calibrated, wide-band

oscilloscope (10-megahertz minimum) at a sweep time of 2.5 milliseconds, and an oscillogram shall be made. The

peak ripple voltage shall not exceed the direct current average voltage by more than 1.5 volts for either polarity (see

4.6.11). Ripple voltage frequency characteristics shall be recorded.

4.6.11 Over-speed. The machine shall be operated as a generator at rated voltage and load at the continuous

operating speed. When the unit has stabilized in temperature, the load shall be removed, the field circuit opened, and

the generator driven to the over-speed rpm specified on the associated specification sheet. The unit shall withstand

five minutes of continuous over-speed operation without signs of mechanical failure, throwing of varnish or solder,

or bearing noise. Upon completion of the over-speed period, the unit shall not show signs of electrical failure as

evidenced by compliance with paragraphs 4.6.4, 4.6.7 and 4.6.10.

4.6.12 Efficiency. The machine shall successfully complete the applicable efficiency tests below.

4.6.12.1 Starter. The machine shall be operated as a starter at a terminal voltage of 28 +0/-1 volts with a torque

load sufficient to produce an armature current equal to the rated current for generator operation. Efficiency of the

machine shall not be less than 70 percent or as specified on the associated specification sheet, whichever is greater.

4.6.12.2 Generator. The machine shall be operated as a generator at rated terminal voltage and loads of 25, 50,

75, 100 and 125 percent in 1000 rpm speed increments between minimum speed for regulation and maximum speed

for regulation (see 4.6.10). The efficiency shall be recorded after temperature stabilization at each speed increment

and up to 125 percent load. The 125 percent load efficiency tests shall commence after temperature stabilization at

full rated load, and shall be completed within five minutes. The efficiency shall not be less than 60 percent or as

specified on the associated specification sheet, whichever is greater.

4.6.13 Cranking torque and speed. If applicable, the machine shall be operated as a starter. The test setup shall

be instrumented to measure the starter drive speeds, drive torque, input current, and voltage specified on the

associated specification sheet in addition to the general instrumentation. The machine shall deliver the specified

torque at the corresponding speeds with the power source(s) indicated on the associated specification sheet. Total

feeder resistance between the starter generator terminals and the power source terminals shall be adjusted to obtain a

voltage drop of 1.8 to 2.0 volts at rated generator current.

4.6.14 Altitude rating chart. The altitude-rating chart furnished by the manufacturer and brush life (for brush

type generators) shall be substantiated during the applicable altitude tests of paragraph 4.6.18.2.